Mr. Spell is based on a popular 1970s Speak & Spell toy by Texas Instruments. He frequently holds or has held seminars on a variety of topics such as "plastic corrosion awareness" and "what to do if you or part of you is swallowed". He also reveals the words he is saying.
He did not play a particularly large role in the first film, but appeared in many background scenes. He played a bigger role near the beginning of the movie when Woody was holding the staff meeting for all the toys. Also, when Andy's friends came to his birthday party, the toys panicked in thinking that they might be replaced with new toys and Mr. Spell, along with basically everyone else aside from Woody, ran to the window in panic to see the size of the presents. Then later, when Andy's friends were running up to his room, Woody told everyone to go back to their places and the toys began to scatter and Mr. Spell can be seen in the overhead shot running in fright and then again behind Mr. Potato Head.
In Toy Story 2, when Buster finds Woody, Mr. Spell displays 13.5, the amount of time in seconds it has elapsed for Buster to find Woody, setting a new record. Later, after Woody is stolen from a yard sale, Mr. Spell helps Andy's toys figure out who has stolen Woody. Mr. Spell also appears in archive footage in the 3rd film.